Field of the Invention
The present invention relates to a hydraulic damping bush or bushing, more particularly in automotive applications, for damping loads in a main loading direction. The hydraulic damping bush or bearing includes an inner sleeve, an outer sleeve, a resilient mounting assembly disposed between inner sleeve and outer sleeve, at least one end cap connecting the inner sleeve to the outer sleeve and capping the space enclosed by the inner sleeve and outer sleeve from the environment, and two chambers charged with a hydraulic damping fluid and interconnected via a transfer duct. The transfer duct has an inlet and an outlet. The main loading direction is oriented parallel to a longitudinal axis of the inner sleeve and outer sleeve. The end caps are formed separate from the resilient mounting assembly and each of the chambers is limited by the resilient mounting assembly or a member adjoining the resilient mounting assembly and by one of the end caps.
Such a bush is disclosed in U.S. Pat. No. 5,005,810. This prior-art axial bush includes an inner sleeve and an outer sleeve interconnected via a resilient mounting assembly. The resilient mounting assembly includes a space that is provided with two chambers separated by a separator. The separator interconnects both chambers via a transfer duct that includes an inlet and an outlet.
A hydraulic damping bush is further described in German Patent Application No. DE 36 12 612 A1. This prior-art bush includes an inner sleeve, an outer sleeve, and a separator including a transfer duct. Provided furthermore are end caps, one of which is produced materially integral with the inner sleeve whilst the other is rigidly connected thereto. To close off the chambers from the environment rubber rings are provided between the end caps and the outer sleeve. The rubber rings must be connected to the end caps and the outer sleeve to provide a seal. Their length varies as a function of the length of the inner sleeve.
Another hydraulic damping bush (mounting) is also described in U.S. Pat. No. 5,890,706. This document discloses a hydraulic mounting that includes an inner sleeve and an outer sleeve interconnected via a resilient (mounting) element in contact with the environment at one end. Provided at the other end of the resilient mounting element and separated by a separator are two chambers charged with a hydraulic fluid. Serving to close off the second chamber from the environment is a thin elastomeric diaphragm (flexible member) integrally configured with the resilient mounting element. Here too, the connection between the resilient mounting element and the elastomeric diaphragm complicate production and assembly.
It is accordingly an object of the invention to provide a hydraulic damping bush that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that permits improved hydraulic damping and that is simple to produce and assemble.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a hydraulic damping bush for damping loads in a main loading direction. The bush includes an inner sleeve, an outer sleeve, a resilient mounting assembly, at least two end caps, two chambers, and a transfer duct. The outer sleeve along with the inner sleeve enclose a space and define a longitudinal direction. The resilient mounting assembly is disposed between the inner sleeve and the outer sleeve. The two end caps connect the inner sleeve to the outer sleeve, cap the space enclosed by the inner sleeve and the outer sleeve, are formed separately from the resilient mounting assembly, and each have a rigid member mutually overlapping in a direction perpendicular to the main loading direction to define an overlapping region. The two chambers are charged with a hydraulic damping fluid. The transfer duct interconnects the two chambers and has an inlet, an outlet, and a main loading direction oriented parallel to the longitudinal axis of the inner sleeve and the outer sleeve. Furthermore, each of the chambers is defined by the resilient mounting assembly, a component adjoining the resilient mounting assembly, or one of the end caps. The inlet and the outlet of the transfer duct are located in the overlapping portion of the rigid members of the resilient mounting assembly and the end caps.
In accordance with a further object of the invention, a bush of the aforementioned kind in that a rigid member of the resilient mounting assembly and a rigid member of the end cap overlap in a direction perpendicular to the main loading direction, wherein the inlet and outlet of the transfer duct are located in the overlapping portion of the rigid members of the resilient mounting assembly and the end caps.
The overlapping of a rigid member of the resilient mounting assembly and the rigid member of the end cap in a direction perpendicular to the main loading direction achieves a pumping effect on movements between the inner sleeve and outer sleeve. This pumping effect facilitates entry of the hydraulic fluid into the transfer duct, enhances the flow through the transfer duct and boosts the hydraulic damping.
The inlet and outlet of the transfer duct are located in the overlapping portion of the rigid members of the resilient mounting assembly and end cap, so that the pumping effect achieved by the overlap on the transfer duct results in a further improvement of the hydraulic damping.
Separately configuring the end caps, on the one hand, and the inner sleeve and outer sleeve as well as the resilient mounting assembly, on the other, now makes it possible to use differing materials as optimized for use in the resilient mounting element or the end caps. The resilient mounting assembly and end caps can now be produced separately and simply assembled in thus resulting in a modular configuration of the bush in accordance with the invention. Preferably, the end caps are also configured separate from the inner sleeve and outer sleeve in this configuration.
The chambers are defined either by the resilient mounting assembly or the end caps or by the components adjoining the resilient mounting assembly and the end caps. These components may be configured more particularly as isolating or plunger components in enabling the response of the bush in accordance with the invention to be adapted to the circumstances in each case.
In this configuration, the resilient mounting assembly is enclosed by the two chambers, the inner sleeve and the outer sleeve with no contact to the environment. In prior-art bushes, the resilient mounting element is always exposed to the environment and thus necessitates use of a special material. This is no longer needed in the bush in accordance with the invention.
In an advantageous further embodiment, the resilient mounting assembly and the end caps are disposed inline in the main loading direction. This results in a simple configuration of the bush in accordance with the invention.
In an advantageous embodiment, the resilient mounting assembly and the end caps are mounted on the inner sleeve and fixed by flanging to the rims of the inner sleeve to thus facilitate assembly. Furthermore, various resilient mounting assemblies and end caps may be combined with each other to thus achieve a modular configuration of the bush.
In an alternative advantageous embodiment, the resilient mounting assembly and inner sleeve are grouped together into a single inner part, on which the end caps are mounted and fixed by flanging the rims of the inner part. Combining the resilient mounting assembly and inner sleeve reduces the number of steps in assembly.
As an alternative, the resilient mounting element may be directly vulcanized to the inner sleeve and outer sleeve so that following mounting of the end caps only the rims need to be flanged in thus furthermore simplifying assembly.
Advantageously, the outer sleeve is fixed by its rims being flanged to make for simple and reliable assembly.
In another advantageous further embodiment, the transfer duct is disposed in the resilient mounting assembly in thus eliminating the need of a separate component for configuring the transfer duct.
The transfer duct may be configured linear and substantially parallel to the main loading direction. This simplifies production whilst improving the flow through the transfer duct in thus achieving enhanced hydraulic damping of the bush in accordance with the invention.
As an alternative, the transfer duct may be configured helical in thus achieving added length and higher damping performance.
To advantage, the bush additionally features a decoupler and/or plunger, as a result of which the response of the bush under load, especially in the higher frequency range, is further enhanced.
In yet another advantageous embodiment, the resilient mounting assembly, and end caps as well as any decoupler or plunger provided, are configured rotationally symmetrical. This rotationally symmetrical configuration results in simplified production and assembly.
In accordance with an advantageous further embodiment, the inner sleeve or inner part is provided with a port for charging the chamber with hydraulic damping fluid. The port is protected by being disposed in the inner sleeve or inner part.
Preferably, the port is closed off by one of the end caps following assembly, i.e. impressing a ball in the port as provided hitherto is now eliminated.
In accordance with an advantageous further embodiment, at least one of the end caps is provided with a port for charging the chamber with hydraulic damping fluid to thus facilitate charging. Ports may also be provided in both the inner sleeve or inner part as well as in one of the end caps.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a hydraulic damping bush, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.